Barbed Wire Fence
Barbed wire fences made from wood and iron can slow down enemies, making them easier to deal with. Place them by using the secondary action.
Repair with Wood and Iron.
Upgrade path
Hit a placed block with a stone axe, claw hammer or nail gun while carrying the material of the next step.
When its hit points run out it becomes 
Barbed Wire Fence, Bloody.
Crafting
Craft at Backpack · makes 1
Harvest drops
Taken apart with a harvesting tool (axe, pickaxe, shovel), before perks and tool bonuses.
Where to find (17 POIs)
Minotaur Theater (tier 5), Navezgane General Hospital (tier 5), Two Bit Tower (tier 5), Good Life Apartments (tier 4), HSP Logistics (tier 4), Pass-N-Gas Store #05 (tier 4), The Fates Motel (tier 4), Water Works (tier 4), Haulwell Freight (tier 3), The Gully Residence (tier 3), The Señor Drogas Residence (tier 3), The McKean Residence (tier 2), Cole's Books (tier 1), The Perkel Residence (tier 1), Camp BBQ, Camp Bravo, Trader Bob.
Points of interest built with this block (any of its variants), the highest tiers first, from the game's prefab files.